What is the white powder on blueberries?

Many people often wonder what the white, chalk-like dusting is on blueberries. “Is that a chemical?”, people ask. The answer to this question is actually quite fascinating. The whitish dust you see on blueberries (and other fruit like grapes and plums) is a naturally occurring substance that is produced by the fruit itself. Often referred to as the “bloom”, this substance is created to protect the blueberry’s skin from insects and harmful bacteria and seals in the moisture to keep the fruit fresher longer. Over time, as the fruit is handled or goes through temperature fluctuations, the powder disappears and the blueberry quickly loses it’s freshness.

Temperature fluctuations are the worst enemy of freshness because they result in the blueberry '“sweating” and immediately losing it’s protective coating. Unfortunately, because of the volume of blueberries that our country consumes, many grocery stores have no other choice but to display their blueberries outside of cold storage for a significant amount of time resulting in poor and inconsistent quality fruit. Blueberries will last much longer if kept between 33-38 degrees and can even handle temperature slightly below 32 degrees without freezing. Although a shiny blueberry might look slightly more appealing than one with a white powder, we always would suggest the blueberry with the “bloom” coating.